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Bicuspid aortic valve: Basics and beyond

Cleveland Clinic Journal of Medicine. 2018 October;85(10):779-784 | 10.3949/ccjm.85a.17069
October 1, 2018|Cleveland Clinic Journal of Medicine
Shailee Y. Shah, MD;Andrew Higgins, MD;Milind Y. Desai, MD, FACC, FAHA, FESC
Author and Disclosure Information

Shailee Y. Shah, MD
Department of Internal Medicine, Cleveland Clinic

Andrew Higgins, MD
Heart and Vascular Institute, Cleveland Clinic

Milind Y. Desai, MD
Haslam Family Endowed Chair in Cardiovascular Medicine, Department of Cardiovascular Medicine, Heart and Vascular Institute, and Department of Diagnostic Radiology, Cleveland Clinic; Professor, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH

Address: Shailee Y. Shah, MD, Department of Internal Medicine, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195; shahs10@ccf.org

ABSTRACT

Bicuspid aortic valve, one of the most common congenital cardiac malformations, is associated with other valvular abnormalities and aortopathies. It increases the risk of thoracic aortic aneurysm and dissection, infective endocarditis, and sudden cardiac death. Patients require regular surveillance for progressive valvular disease and aortopathy. Although bicuspid aortic valve may occur sporadically, many cases are inherited, so first-degree relatives should be evaluated and genetic counseling considered.

KEY POINTS

  • Associated aortopathies such as aortic root dilation, aneurysm, dissection, and coarctation may initially be asymptomatic.
  • Regular surveillance with transthoracic echocardiography (TTE) is required.
  • Transesophageal echocardiography should be performed if TTE does not clearly show the aorta and aortic root. Magnetic resonance imaging or computed tomographic angiography may also be needed to measure the aortic root and ascending thoracic aorta.
  • If initial imaging is normal and there is no aortic dilation, repeat imaging should be done every 5 to 10 years. If any abnormality is found, annual surveillance is needed.
  • Women with a bicuspid aortic valve who are contemplating pregnancy should undergo echocardiography first, and some may need to undergo surgery.

DISEASE PROGRESSION

Although bicuspid aortic valve is typically asymp­tomatic at first, it is commonly associated with progressive valvulopathy and thoracic aortic disease.1,3,4,15 It can lead to chronic heart failure and increase the risk of acute aortic syndromes and sudden cardiac death.15

Michelena et al16 studied 212 cases of asymp­tomatic bicuspid aortic valve. Although the survival rate 20 years after diagnosis was the same as for an age-matched cohort in the general population, the frequency of adverse cardiovascular events and surgical interventions was higher.

Aortic stenosis progresses rapidly

Aortic stenosis associated with a bicuspid aortic valve tends to affect younger patients and progress more rapidly than when associated with a tricuspid valve.17

In a study of 542 patients with congenital bicuspid aortic valve undergoing aortic valve replacement,3 75% had isolated aortic stenosis, 10% had aortic stenosis with some degree of aortic insufficiency, and 13% had isolated aortic insufficiency. Given the tendency of aortic stenosis to progress rapidly, early surgery is often pursued.17,18

Aneurysmal disease is common

The thoracic aorta is at increased risk of aneurysmal disease, coarctation, and dissection in patients with a bicuspid aortic valve.1,6,15

Michelena et al16 reported that in patients without an aneurysm at the time of bicuspid aortic valve diagnosis, the 25-year risk of aneurysm formation was approximately 26%. In patients with an aneurysm at the time of diagnosis, the 15-year risk of aortic surgery after the diagnosis of aneurysm was about 46% and the risk of aortic dissection after aneurysm diagnosis was 7%.15 Compared with the general population, the age-adjusted relative risk of aortic aneurysm in patients with bicuspid aortic valve was 86.2, and that of aortic dissection was 8.4. Although the absolute incidence of dissection is low in these patients, it is markedly higher than in the general population, particularly in older patients (age > 50) and those with an aneurysm at the time of diagnosis.15

The risk of infective endocarditis

Patients with bicuspid aortic valve are highly prone to infective endocarditis for reasons that remain poorly understood. The pathogens in most cases are staphylococci or viridans streptococci.19 Patients with infective endocarditis typically require emergency surgery. Complications including valvular abscess, myocardial abscess, and overt heart failure are common.19

Lamas and Eykyn20 studied 408 cases of native valve endocarditis; in 12.3%, the patient had a bicuspid aortic valve. In this subset, all were male, the mean age was 39 at diagnosis, 82% needed surgery, and the death rate was 14%.

Patients with bicuspid aortic valve do not routinely need antibiotics before dental and surgical procedures, but if they have had endocarditis in the past, they need antibiotics to prevent a recurrence.21

REGULAR MONITORING NEEDED

Because complications may be life-threatening, early detection of progressive disease by regular screening is critical. Echocardiographic evaluation of valvular function, ventricular dimensions and function, and diameter of the aortic root and ascending aorta should be performed in every patient with bicuspid aortic valve. If initial imaging is normal and there is no aortic dilation, imaging should be repeated every 5 to 10 years. If any abnormality is found, repeat imaging is needed every year.22

Transthoracic echocardiography
Figure 1. Transthoracic echocardiography, parasternal long-axis view, shows a dilated aortic root (AR) measuring 4.5 cm in a patient with bicuspid aortic valve (arrows). AA, ascending aorta; LA, left atrium; LV, left ventricle.

Two-dimensional transesophageal echocardiography
Figure 2. Two-dimensional transesophageal echocardiography demonstrates an anterior-posterior bicuspid aortic valve (opening phase, arrows). RA, right atrium; LA, left atrium; RV, right ventricle.

Magnetic resonance imaging (MRI) or computed tomographic (CT) angiography may be required to better assess the aorta for patients requiring a surgical intervention, or when aortic dimensions are not clearly visualized on TTE. MRI has 2 advantages over CT angiography: it poses no radiation risk, and it provides more information on left ventricular function and dimensions, in addition to valve assessment.23,24

No published study has compared MRI or CT angiography and transesophageal echocardiography (TEE), but in a study of 174 patients with dilated aortic root, combined TTE and TEE detected aortic valve morphology accurately in 98% of cases. As TEE is more invasive, it is not recommended for regular surveillance (Figures 1 and 2).25

FAMILY SCREENING RECOMMENDED

Close relatives should be evaluated for aortic valve and thoracic aortic disease.12,13,23,26

The American College of Cardiology (ACC) and the American Heart Association (AHA), backed by radiologic and cardiovascular associations, concur in recommending echocardiographic screening and routine screening of the thoracic aorta for aortic root dilation in first-degree relatives (ie, siblings, parents, and children) of patients with bicuspid aortic valve (class I recommendation).22,27,28

A comprehensive physical examination is recommended for family members in addition to TTE, with careful assessment of the aortic valve in short and long axes, and of the aortic root.14 If the aorta cannot be adequately evaluated with TTE, further assessment should be pursued with CT angiography or MRI.

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